Guralp Systems CMG-DM24 - Manual (Page 8)

Operator’s Guide DM-24 Digitiser
Issue G January 2003 6
output of the sensor cannot be contaminated and is easily processed, stored and
transmitted over long data links.
The stand-alone configuration with (differential) analogue inputs can interface with
other sensor systems.
There are two different types of housings used for the stand-alone DM24 digitiser. The
water proof housing introduces in 2003 is shown below. The operation of the digitiser is
identical to those digitisers used prior to 2003. The housing of the digitiser is from high
impact copolymer polypropylene with external inputs mil.spec connectors fitted on to a
metal plate. The digitiser housing also has internal cable storage facility.
Stand-alone configurations are supplied within a portable waterproof housing as shown
in the photograph above or optionally in a 19” rack mounted enclosure. In both cases
the digitiser units are fitted with high impedance low noise differential input pre-
amplifier modules.
The stand-alone CMG-DM24 unit input connections are identical to the output
connections of the Guralp CMG-1T, CMG-3T, CMG-3ESP and CMG-40T. Indeed
other sensors can also be wired to the CMG-DM24.
The purpose of creating a compatible connection between the CMG-DM24 and CMG
sensors is to ensure that all the broadband seismometer commands can be initiated
through the CMG-DM24 module.
Generally the CMG-DM24 module has 1 to 3 analogue to digital converters with 24-bit
resolution. However, the CMG-DM24 stand-alone units can have 3 or 6 digitiser
channels with 24-bit resolution. There are no operational differences between the 3
channel and 6 channel CMG-DM24 systems.
ENVIRONMENTAL CHANNELS
An optional 16 channel 16 bit digitiser module can be included in the main digitiser unit
to provide low sample rate data (4 s/s) primarily used for ‘State of Health’ monitoring
e.g. sensor mass position, temperature, pressure, battery voltage etc. This data is
packaged and processed in exactly the same fashion as the primary digitiser channels.